Method and device for transmitting video data

Abstract

This method allows the transmission of coded data representing a sequence of digital images. A predetermined quantity of this data is stored in a buffer before transmission over a communication network. The method comprises a step of determining a subset of data in the buffer to be transcoded, as a function of at least one quantity representing the bandwidth available for the communication network.

1. A method of transmitting coded data representing a sequence of digital images, a predetermined quantity of said data being stored in a buffer memory before transmission over a communication network, said method comprising a step of determining a subset of data representing a subset of successive images of the sequence of digital images in said buffer memory to be transcoded, as a function of at least one quantity representing a bandwidth available for said communication network;
 wherein the determination step comprises a sub-step of calculating a pair of parameters (K,X1) where the parameter K represents the index of the first image to be transcoded and X1 represents the number of images to be transcoded. 
 
     
     
       2. A method according to  claim 1 , wherein said step of calculating the pair of parameters (K,X1) comprises a step consisting of calculating the value of K as small as possible and the value of a parameter X as large as possible so as always to have i(t)<n(t), X being the number of images that it is possible to transcode, i(t) designating the index of the image currently being transmitted as a function of time and n(t) designating the index of the image currently being transcoded as a function of time. 
     
     
       3. A method according to  claim 2 , wherein the index n(t) of the image currently being transcoded is given by: 
       
         
           
             
               
                 n 
                 ⁡ 
                 
                   ( 
                   t 
                   ) 
                 
               
               = 
               
                 
                   i 
                   + 
                   K 
                   + 
                   
                     
                       ⌊ 
                       
                         
                           t 
                           - 
                           
                             t 
                             0 
                           
                         
                         
                           t 
                           1 
                         
                       
                       ⌋ 
                     
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     if 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       t 
                       0 
                     
                   
                 
                 ≤ 
                 t 
                 < 
                 
                   
                     t 
                     0 
                   
                   + 
                   
                     X 
                     . 
                     
                       t 
                       1 
                     
                   
                 
               
             
           
         
         where the sign └ ┘ designates the integer part, t 0  designates the decision time where the number X1 of images to be transcoded is estimated, i designates the index of the image currently being transmitted at time t 0  and t 1  designates the duration of transcoding of an image. 
       
     
     
       4. A method according to  claim 1 , wherein, when the data is transmitted by a network card, the quantity representing the available bandwidth is a measure of flow of the network card. 
     
     
       5. A method according to  claim 1 , wherein the data to be transcoded are packets corresponding to blocks of images that are not used for the coding of other images in the sequence of images. 
     
     
       6. A method according to  claim 1 , wherein the data to be transcoded are images in the sequence of images. 
     
     
       7. A method according to  claim 6 , wherein the last image to be transcoded is situated before an image coded in “Intra” mode in the sequence of images. 
     
     
       8. An information storage means readable by a computer or a microprocessor storing instructions of a computer program, allowing the implementation of a transmission method according to  claim 1 . 
     
     
       9. An information storage means according to  claim 8 , being partially or totally removable. 
     
     
       10. A device for transmitting coded data representing a sequence of digital images, a predetermined quantity of said data being stored in a buffer memory before transmission on a communication network, said device comprising:
 means for determining a subset of data representing a subset of successive images of the sequence of digital images in said buffer memory to be transcoded, as a function of at least one quantity representing a bandwidth available for said communication network, wherein said determination means comprise means of calculating a pair of parameters (K,X1) where the parameter K represents the index of the first image to be transcoded and X1 represents the number of images to be transcoded; and 
 transmission means for transmitting coded data. 
 
     
     
       11. A device according to  claim 10 , wherein said means of calculating the pair of parameters (K,X1) comprise means for calculating the value of K as small as possible and the value of a parameter X as large as possible so as always to have i(t)<n(t), X being the number of images that it is possible to transcode, i(t) designating the index of the image currently being transmitted as a function of time and n(t) designating the index of the image currently being transcoded as a function of time. 
     
     
       12. A non-transitory computer program product loadable into a programmable apparatus, comprising sequences of instructions for implementing a transmission method when said program is loaded into and run by said programmable apparatus, the transmission method for transmitting coded data representing a sequence of digital images, a predetermined quantity of said data being stored in a buffer memory before transmission over a communication network, said transmission method comprising a step of determining a subset of data representing a subset of successive images of the sequence of digital images in said buffer memory to be transcoded, as a function of at least one quantity representing a bandwidth available for said communication network;
 wherein the determination step comprises a sub-step of calculating a pair of parameters (K,X1) where the parameter K represents the index of the first image to be transcoded and X1 represents the number of images to be transcoded. 
 
     
     
       13. A method of transmitting coded data representing a sequence of digital images, a predetermined quantity of said data being stored in a buffer memory before transmission over a communication network, said method comprising a step of determining a number of images of the sequence of digital images in said buffer memory to be transcoded, as a function of a quantity representing a bandwidth available for said communication network and a quantity representing a size of the images already coded and present in said buffer memory;
 wherein the determination step comprises a sub-step of calculating a pair of parameters (K,X1) where the parameter K represents the index of the first image to be transcoded and X1 represents the number of images to be transcoded.